Methadone: general

Methadone is a synthetic opioid (molecular formula C21H27NO), made as a racemic mixture of two mirror-image forms, (R)- and (S)-methadone [1][2]. It's used both as a pain reliever and as a long-term treatment for opioid use disorder [1][3]. In the US it's FDA-approved for moderate-to-severe pain that hasn't responded to non-opioid medication, or when other opioids haven't worked [3]. It was first synthesized by German scientists during World War II in response to a morphine shortage, and reached the US in 1947 as a painkiller [4][5]. It has since been used for over forty years as a detox and maintenance treatment for opioid addiction, and is the most studied medication for opioid use disorder [4][6].

Methadone's half-life can vary from 8 to 59 hours depending on the person, with an average of around 24 hours [6].

As with opioids generally, opioids bind to receptors in the brain that regulate breathing, and overdose happens when that signal is interrupted enough that breathing slows and can stop [7]. As with opioids as a class, this is reversible with naloxone and basic life support if given in time [8]. Naloxone has little effect on someone who hasn't taken opioids [8].

References

1. Methadone | C21H27NO | CID 4095 - PubChem — National Center for Biotechnology Information (NCBI)
2. methadone | Ligand page | IUPHAR/BPS Guide to PHARMACOLOGY — IUPHAR/BPS Guide to Pharmacology
3. Methadone - StatPearls - NCBI Bookshelf — National Center for Biotechnology Information (NCBI)
4. METHADONE (Trade Names: Methadose®, Dolophine®; Street Names: Fizzies, Amidone, Chocolate Chip Cookies) — Drug Enforcement Administration (DEA) Diversion Control Division
5. Methadone for Chronic Pain: A Review of Pharmacology, Efficacy, and Safety Concerns - PMC — National Institutes of Health (NIH)
6. Chapter 3B: Methadone - Medications for Opioid Use Disorder - NCBI Bookshelf — National Center for Biotechnology Information (NCBI)
7. Opioid Overdose: Signs, Symptoms & Treatment — Cleveland Clinic
8. Opioid overdose — World Health Organization